Our core switches are 5406Rzl2 each with dual management modules. I was under the impression that I could upgrade the code (using some mix of redundancy and other features) with minimal downtime. Around the Internet, I've seen various ramblings of things tried but never any definite yes or no. Is there a way to accomplish this?
The 5400R has dual management modules for redundancy (if one MM fails, the second takes over instantaneously), which can also be used to perform switch software upgrades with reduced downtime by loading a new software image, booting the standby MM onto the new version, then performing a redundancy switchover to swap to the standby MM.
If you have a pair of 5400Rs stacked using VSF (front plane stacking), the VSF Fast Software Upgrade feature uses an automated sequenced reboot process to minimize downtime for devices with redundant links (at least one link per VSF member chassis).
I'm hoping to try this during our maintenance window next week, but according to TAC...
#copy sftp flash user ftpuser ftp.server.ip KB_16_08_0003.swi secondary
#boot set-default flash primary
#show redundancy (wait for sync)
...will upgrade with very little to no downtime. In their lab, there were no pings dropped. I'll add my results next week.